Which of the following molecules are polar? a. BFCl2 b. CH3CH2CH2CH2CH2CH3 c. TeF3- d. GeF2H2
The Correct Answer and Explanation is:
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Correct Answer: a. BFCl₂, c. TeF₃⁻, and d. GeF₂H₂ are polar molecules.
Explanation:
Polarity in molecules depends on both bond polarity (differences in electronegativity between atoms) and molecular geometry (shape). A molecule is polar if it has a net dipole moment due to asymmetrical charge distribution.
a. BFCl₂ – Polar
BFCl₂ has a trigonal planar geometry with one boron atom bonded to one fluorine and two chlorine atoms. Fluorine is more electronegative than chlorine, so the B–F bond is more polar than the B–Cl bonds. Because the atoms are not identical and the geometry is not symmetrical with respect to the electronegativities, their dipoles do not cancel. This creates a net dipole, making the molecule polar.
b. CH₃CH₂CH₂CH₂CH₂CH₃ (hexane) – Nonpolar
This is a straight-chain alkane with only C–C and C–H bonds. The electronegativity difference between carbon and hydrogen is small, and the molecule has a symmetrical structure. Therefore, any small bond dipoles cancel out. The molecule has no net dipole, making it nonpolar.
c. TeF₃⁻ – Polar
Tellurium trifluoride has three bonding pairs and one lone pair, giving it a trigonal pyramidal shape (similar to NH₃). This geometry is not symmetrical, and fluorine is highly electronegative. The lone pair on tellurium adds to the asymmetry, so the molecule has a net dipole moment, making it polar.
d. GeF₂H₂ – Polar
Germanium tetra-atom compound with two fluorine atoms and two hydrogen atoms likely has a tetrahedral structure. Since fluorine is much more electronegative than hydrogen, the bond dipoles do not cancel out due to the asymmetrical placement of atoms with different electronegativities. The molecule has a net dipole, so it is polar.
Summary:
- Polar: a. BFCl₂, c. TeF₃⁻, d. GeF₂H₂
- Nonpolar: b. CH₃CH₂CH₂CH₂CH₂CH₃
